LIQUID-CRYSTALLINE MEDIUM

Abstract

A liquid-crystalline media comprising one or more compounds of formula S

##STR00001## where the parameters have the meaning defined in claim 1, and one or more compounds of the formula I and one or more compounds of the formula II or one or more compounds of the formula I and one or more compounds of the formula III or one or more compounds of the formula II and one or more compounds of the formula III or one or more compounds of the formula I and one or more compounds of the formula II and one or more compounds of the formula III:

##STR00002##

in which the parameters have the meaning indicated in claim 1, and to components comprising these media for high-frequency technology, in particular phase shifters and microwave array antennas.

Claims

1. Liquid-crystal medium, characterized in that it comprises one or more compounds of formula S ##STR00153## in which n denotes 1 or 2, m denotes (4-n), denotes an organic radical having 4 bonding sites, Z.sup.1 and Z.sup.2 independently of one another, denote O, (C?O), (NR.sup.4) or a single bond, but do not both simultaneously denote O, r and s, independently of one another, denote 0 or 1, Y.sup.1 to Y.sup.4 independently of one another, denote alkyl having 1 to 4 C atoms and alternatively, also independently of one another, one or both of the pairs (Y.sup.1 and Y.sup.2) and (Y.sup.3 and Y.sup.4) together denote a divalent group having 3 to 6 C atoms, R.sup.1 denotes H, O.sup.?, OR.sup.3, or OH, R.sup.2 on each occurrence, independently of one another, denotes H, F, OR.sup.4, NR.sup.4R.sup.5, a straight-chain or branched alkyl chain having 1-20 C atoms, in which one CH.sub.2 group or a plurality of CH.sub.2 groups may be replaced by O or C(?O), but two adjacent CH.sub.2 groups cannot be replaced by O, or denotes a hydrocarbon radical which contains a cycloalkyl or alkylcycloalkyl unit, and in which one CH.sub.2 group or a plurality of CH.sub.2 groups may be replaced by O or C(?O), but two adjacent CH.sub.2 groups cannot be replaced by O, and in which one H atom or a plurality of H atoms may be replaced by OR.sup.4, N(R.sup.4)(R.sup.5) or R.sup.6, or denotes an aromatic or heteroaromatic hydrocarbon radical, in which one H atom or a plurality of H atoms may be replaced by OR.sup.4, N(R.sup.4)(R.sup.5) or R.sup.6, R.sup.3 on each occurrence, independently of one another, denotes a straight-chain or branched alkyl chain having 1-20 C atoms, in which one CH.sub.2 group or a plurality of CH.sub.2 groups may be replaced by O or C(?O), but two adjacent CH.sub.2 groups cannot be replaced by O, or denotes a hydrocarbon radical which contains a cycloalkyl or alkylcycloalkyl unit, and in which one CH.sub.2 group or a plurality of CH.sub.2 groups may be replaced by O or C(?O), but two adjacent CH.sub.2 groups cannot be replaced by O, and in which one H atom or a plurality of H atoms may be replaced by OR.sup.4, N(R.sup.4)(R.sup.5) or R.sup.6, or denotes an aromatic or heteroaromatic hydrocarbon radical, in which one H atom or a plurality of H atoms may be replaced by OR.sup.4, N(R.sup.4)(R.sup.5) or R.sup.6, or can be ##STR00154## (1,4-cyclohexylene), in which one or more CH.sub.2 groups may be replaced by O, CO or NR.sup.4, or an acetophenyl, isopropyl or 3-heptyl radical, R.sup.4, R.sup.5 on each occurrence, independently of one another, denotes a straight-chain or branched alkyl or acyl group having 1 to 10 C atoms or an aromatic hydrocarbon or carboxyl radical having 6-12 C atoms, R.sup.6 on each occurrence, independently of one another, denotes a straight-chain or branched alkyl group having 1 to 10 C atoms, in which one CH.sub.2 group or a plurality of CH.sub.2 groups may be replaced by O or C(?O), but two adjacent CH.sub.2 groups cannot be replaced by O, and one or more compounds of the formula I and one or more compounds of the formula II or one or more compounds of the formula I and one or more compounds of the formula III or one or more compounds of the formula II and one or more compounds of the formula III or one or more compounds of the formula I and one or more compounds of the formula II and one or more compounds of the formula III: ##STR00155## in which L.sup.11 denotes R.sup.11 or X.sup.11, L.sup.12 denotes R.sup.12 or X.sup.12, R.sup.11 and R.sup.12, independently of one another, denote H, unfluorinated alkyl or unfluorinated alkoxy having 1 to 15 C atoms or unfluorinated alkenyl, unfluorinated alkenyloxy or unfluorinated alkoxyalkyl having 2 to 15 C atoms, X.sup.11 and X.sup.12, independently of one another, denote H, F, Cl, CN, NCS, SF.sub.5, fluorinated alkyl or fluorinated alkoxy having 1 to 7 C atoms or fluorinated alkenyl, unfluorinated alkenyloxy or unfluorinated or fluorinated alkoxyalkyl having 2 to 7 C atoms, and ##STR00156## independently of one another, denote ##STR00157## in which L.sup.21 denotes R.sup.21 and, in the case where Z.sup.21 and/or Z.sup.22 denote trans-CH?CH or trans-CF?CF, alternatively denotes X.sup.21, L.sup.22 denotes R.sup.22 and, in the case where Z.sup.21 and/or Z.sup.22 denote trans-CH?CH or trans-CF?CF, alternatively denotes X.sup.22, R.sup.21 and R.sup.22, independently of one another, denote H, unfluorinated alkyl or unfluorinated alkoxy having 1 to 17, preferably having 3 to 10, C atoms or unfluorinated alkenyl, unfluorinated alkenyloxy or unfluorinated alkoxyalkyl having 2 to 15, preferably 3 to 10, C atoms, X.sup.21 and X.sup.22, independently of one another, denote F or Cl, CN, NCS, SF.sub.5, fluorinated alkyl or fluorinated alkoxy having 1 to 7 C atoms or fluorinated alkenyl, fluorinated alkenyloxy or fluorinated alkoxyalkyl having 2 to 7 C atoms, one of Z.sup.21 and Z.sup.22 denotes trans-CH?CH, trans-CF?CF or C?C and the other, independently thereof, denotes trans-CH?CH, trans-CF?CF or a single bond, and ##STR00158## independently of one another, denote ##STR00159## in which L.sup.31 denotes R.sup.31 or X.sup.31, L.sup.32 denotes R.sup.32 or X.sup.32, R.sup.31 and R.sup.32, independently of one another, denote H, unfluorinated alkyl or unfluorinated alkoxy having 1 to 17 C atoms or unfluorinated alkenyl, unfluorinated alkenyloxy or unfluorinated alkoxyalkyl having 2 to 15 C atoms, X.sup.31 and X.sup.32, independently of one another, denote H, F, Cl, CN, NCS, SF.sub.5, fluorinated alkyl or fluorinated alkoxy having 1 to 7 C atoms or fluorinated alkenyl, unfluorinated or fluorinated alkenyloxy or unfluorinated or fluorinated alkoxyalkyl having 2 to 7 C atoms, Z.sup.31 to Z.sup.33, independently of one another, denote trans-CH?CH, trans CF?CF, C?C or a single bond, and ##STR00160## independently of one another, denote ##STR00161## and optionally one or more further compounds.

2. Liquid crystal medium according to claim 1 characterized in that n in formula S denotes 2.

3. Liquid crystal medium according to claim 1, characterized in that it comprises one or more compounds of the formula I, as indicated in claim 1.

4. Liquid-crystal medium according to claim 1, characterized in that it comprises one or more compounds of the formula II, as indicated in claim 1.

5. Liquid-crystal medium according to claim 1, characterized in that it comprises one or more compounds of the formula III, as indicated in claim 1.

6. Liquid-crystal medium according to claim 3, characterized in that the concentration of the compounds of the formula I in the medium is in the range from in total 15% to 70%.

7. Liquid-crystal medium according to claim 4, characterized in that the concentration of the compounds of the formula II in the medium is in the range from in total 1% to 60%.

8. Liquid-crystal medium according to claim 3, characterized in that it comprises one or more compounds selected from the group of the compounds of the formulae I-1 to I-3: ##STR00162##

9. Liquid crystal medium according to claim 1, characterized in that the one or more compounds of formula I are selected from the compounds of the formulae S1-1 and S2-1. ##STR00163##

10. Component for high-frequency technology, characterized in that it comprises a liquid crystal medium according to claim 1.

11. Component according to claim 10, characterized in that it is suitable for operation in the microwave range.

12. Component according to claim 10, characterized in that it is a phase shifter.

13. (canceled)

14. Process for the preparation of a liquid-crystal medium, characterized in that one or more compounds of the formula I, as indicated in claim 1, are mixed with one or more compounds selected from the group of the compounds of the formulae II and/or III, and S, as indicated in claim 1, and optionally with one or more further compounds and/or with one or more additives.

15. Microwave antenna array, characterized in that it comprises one or more components according to claim 10.

Description

EXAMPLES

[0417] The following examples illustrate the present invention without limiting it in any way.

[0418] However, it is clear to the person skilled in the art from the physical properties what properties can be achieved and in what ranges they can be modified. In particular, the combination of the various properties which can preferably be achieved is thus well defined for the person skilled in the art.

[0419] Irradiation experiments are performed in glass capillary tubes of 0.4 mm glass thickness. After the liquid crystal is filled into the tube the tube is irradiated with a total dose of gamma ray of 300 krad, which corresponds to 15-30 years of operation in space. The clearing temperatures of the samples are measured before and after irradiation.

Examples 1.1 to 1.4

[0420] The following mixture (M-1) is prepared and investigated.

TABLE-US-00008 Mixture M-1 Composition Compound Concentration/ No. Abbreviation % by weight 1 PPTUI-3-2 20.0 2 PPTUI-3-4 36.0 3 GGP-3-CL 10.0 4 GGP-5-CL 20.0 5 CPGP-5-2 7.0 6 CPGP-5-3 7.0 ? 100.0 Physical properties T(N, I) = 173.0? C. ?n(20? C., 589 nm) = 0.3348 ??(20?, 1 kHz) = 4.0 ?.sub.1(20? C.) = 727 mPa .Math. s k.sub.11(20? C.) = 23.5 pN k.sub.33(20? C.) = 32.0 pN

[0421] Mixture M-1 is divided into ten parts. First, as a reference (ref.), the clearing temperature of the unstabilised mixture is measured before and after irradiation. Next, the remaining parts are use to prepare the stabilised mixtures given in table 1 using the stabilisers of formula S1-1 and S2-1 in the amounts given in table 1. Again, the clearing temperatures are measured before and after irradiation.

TABLE-US-00009 TABLE 1 c(Stab.)/ T.sub.(N, I) Example Mixture Stabiliser ppm before after (Ref.) M-1 none 0 173.0 163.0 1.1 M-1-1 S1-1 100 173.0 165.0 1.2 M-1-2 S1-1 500 173.0 172.0 1.3 M-1-3 S2-1 100 173.0 164.5 1.4 M-1-4 S2-1 500 173.0 172.5

[0422] A lower clearing temperature after irradiation means some damage to the liquid crystal.

[0423] As can be seen from the results given in table 1, the unstabilised mixture M-1 suffers from a serious drop of the clearing temperature upon irradiation. A small amount of 100 ppm of either compound S1-1 or S2-1 already shows a stabilising effect. The use of 500 ppm of S1-1 or S2-1 results, within the error limits, in complete stabilisation against gamma ray irradiation.